/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2009 OpenVPN Technologies, Inc. <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "syshead.h"

#include "proto.h"
#include "error.h"

#include "memdbg.h"

/*
 * If raw tunnel packet is IPv4, return true and increment
 * buffer offset to start of IP header.
 */
bool
is_ipv4 (int tunnel_type, struct buffer *buf)
{
  int offset;
  const struct openvpn_iphdr *ih;

  verify_align_4 (buf);
  if (tunnel_type == DEV_TYPE_TUN)
    {
      if (BLEN (buf) < (int) sizeof (struct openvpn_iphdr))
	return false;
      offset = 0;
    }
  else if (tunnel_type == DEV_TYPE_TAP)
    {
      const struct openvpn_ethhdr *eh;
      if (BLEN (buf) < (int)(sizeof (struct openvpn_ethhdr)
	  + sizeof (struct openvpn_iphdr)))
	return false;
      eh = (const struct openvpn_ethhdr *) BPTR (buf);
      if (ntohs (eh->proto) != OPENVPN_ETH_P_IPV4)
	return false;
      offset = sizeof (struct openvpn_ethhdr);
    }
  else
    return false;

  ih = (const struct openvpn_iphdr *) (BPTR (buf) + offset);

  if (OPENVPN_IPH_GET_VER (ih->version_len) == 4)
    return buf_advance (buf, offset);
  else
    return false;
}

#ifdef PACKET_TRUNCATION_CHECK

void
ipv4_packet_size_verify (const uint8_t *data,
			 const int size,
			 const int tunnel_type,
			 const char *prefix,
			 counter_type *errors)
{
  if (size > 0)
    {
      struct buffer buf;

      buf_set_read (&buf, data, size);

      if (is_ipv4 (tunnel_type, &buf))
	{
	  const struct openvpn_iphdr *pip;
	  int hlen;
	  int totlen;
	  const char *msgstr = "PACKET SIZE INFO";
	  unsigned int msglevel = D_PACKET_TRUNC_DEBUG;

	  if (BLEN (&buf) < (int) sizeof (struct openvpn_iphdr))
	    return;
  
	  verify_align_4 (&buf);
	  pip = (struct openvpn_iphdr *) BPTR (&buf);
	  
	  hlen = OPENVPN_IPH_GET_LEN (pip->version_len);
	  totlen = ntohs (pip->tot_len);
	  
	  if (BLEN (&buf) != totlen)
	    {
	      msgstr = "PACKET TRUNCATION ERROR";
	      msglevel = D_PACKET_TRUNC_ERR;
	      if (errors)
		++(*errors);
	    }

	  msg (msglevel, "%s %s: size=%d totlen=%d hlen=%d errcount=" counter_format,
	       msgstr,
	       prefix,
	       BLEN (&buf),
	       totlen,
	       hlen,
	       errors ? *errors : (counter_type)0);
	}
    }
}

#endif
